The present invention relates to a fuel injection control apparatus for use in a fuel injection system of an internal combustion engine and, more particularly, to a fuel injection control apparatus suitable for use in an electronic fuel injection system for an automotive gasoline engine.
In an internal combustion engine, such as a gasoline engine etc., an attempt for obtaining a high compression ratio for the engine is effective in providing an improved thermal efficiency in operation of the engine. However, the attempt for obtaining a high compression ratio for the engine is accompanied by a problem of knocking.
Up to now, there have been tried various proposals an techniques which attempt to heighten the compression ratio for the engine without creating knocking. For example, there has been known a method in which the knocking occurrence is maintained at a critical condition by controlling the ignition time using a knock sensor.
Further, there has been known a method in which the air-fuel mixture ratio (air-fuel ratio (A/F)) is maintained at the rich side at a surrounding portion of a spark plug by controlling the air-fuel mixture ratio distribution in the cylinder. This latter stated technique is disclosed, for example, in Japanese Patent Laid-Open Publication No. 179328/1982.
As is generally known, knocking in an internal engine combustion results from a phenomenon in which a wall surface of some portion of an inner surface in a combustion chamber, such as a wall surface of the cylinder or an upper surface of the piston, is ignited prior to the ignition of the air-fuel mixture by the spark plug. To avoid this problem, it is effective to lower the ignition characteristic property of the air-fuel mixture.
Besides, from an aspect of stabilization of the combustion of the engine, it is desirable to improve the ignition characteristic property of the air-fuel mixture. When the combustion for the engine is unstable, the combustion efficiency for the engine becomes lower, and the fuel consumption for the engine becomes lower also.
Regarding the above stated conventional techniques concerning fuel injection control, there is a problem in attaining a desired combustion efficiency for the engine at the ignition time, and further there is no consideration is given to the complicated air-fuel ratio (A/F) control accompanying the control for the air-fuel mixture distribution.
In the fuel injection system for a gasoline engine, the fuel included in the air-fuel mixture is constituted mainly, of a gasoline spray which floats in air in the cylinder in a droplet state, or in the state of a gasoline spray.